275/300N*

[kcd1184]

Just curious as to how the extra 25 hp is created between the 275hp and the 300hp Northstar motor. I know the axel ratios are different, but not hp related. I just bought a 98 275hp Eldo and I have a 270hp 94 Eldo.

[Cadillac Jim]

The only parts that are different between the 275 hp (VIN "Y") and 300 hp (VIN "9") Northstars is the intake cams, so far as I know. The axle ratio is different, as are the programs and tuning data in the PCM, and a PCM for one will throw a P0730 "Incorrect Gear Ratio" code as well as give you other codes and driveability problems. At this late date the prices are so low on pre-2000 cars that it would be simpler and cheaper to trade a VIN "Y" car for a VIN "9" car than to try to convert one.

On the other hand, I have seen horsepower curves on SLS cars that clearly show that they do not have VIN "Y" cams, or even OEM cams at all. So, it can be done. You will likely need the help of someone fluent with a Tech II on your model car to smooth out the wrinkles, and there is no guarantee of success in terms of getting a nice daily driver without driveability issues such as inappropriate shift points or no guts at low RPM with a quick shift to second gear.

For what it's worth, the VIN "9" engine came first, in the 1993 1/2 Allante and the 1994 STS/ETC. The VIN "Y" engine came a year or two later. The Allante with the Northstar was the pace car for the Indianapolis 500 in 1993.

[BodybyFisher]

Just curious as to how the extra 25 hp is created between the 275hp and the 300hp Northstar motor. I know the axel ratios are different, but not hp related. I just bought a 98 275hp Eldo and I have a 270hp 94 Eldo.

The difference between the 270 hp 94 and the 275 hp engine was the intake. Jim gave a good summary above between the 275 and 300

[KHE]

For what it's worth, the VIN "9" engine came first, in the 1993 1/2 Allante and the 1994 STS/ETC. The VIN "Y" engine came a year or two later. The Allante with the Northstar was the pace car for the Indianapolis 500 in 1993.

Actually, the Northstar engine was designed at 270 HP. GM marketing wanted a higher HP version (close to 300HP) late in the development. The 295 HP engine was created by using a different lift/duration on the cam lobes and thus the VIN 9 engine. With the introduction of the plastic intake, the HP for each was increased by 5 HP.

While it is true the 295 HP was out first, it was developed after the 270 HP variant. The '94 Base Eldorado and Seville got the original design intent 270 HP engine and the base Deville got the 275 HP engine in '96.

[Cadillac Jim]

I stand corrected, KHE. Note from the cam specs in the FSM that the intake and exhaust cam lift and duration are identical in the VIN "9" engines, a common thing seen in some high performance street cams from Crane, Crower, and others.

[kcd1184]

The only parts that are different between the 275 hp (VIN "Y") and 300 hp (VIN "9") Northstars is the intake cams, so far as I know. The axle ratio is different, as are the programs and tuning data in the PCM, and a PCM for one will throw a P0730 "Incorrect Gear Ratio" code as well as give you other codes and driveability problems. At this late date the prices are so low on pre-2000 cars that it would be simpler and cheaper to trade a VIN "Y" car for a VIN "9" car than to try to convert one.

On the other hand, I have seen horsepower curves on SLS cars that clearly show that they do not have VIN "Y" cams, or even OEM cams at all. So, it can be done. You will likely need the help of someone fluent with a Tech II on your model car to smooth out the wrinkles, and there is no guarantee of success in terms of getting a nice daily driver without driveability issues such as inappropriate shift points or no guts at low RPM with a quick shift to second gear.

For what it's worth, the VIN "9" engine came first, in the 1993 1/2 Allante and the 1994 STS/ETC. The VIN "Y" engine came a year or two later. The Allante with the Northstar was the pace car for the Indianapolis 500 in 1993.

Don't want to get more horses, just was curious. I had been looking around for a while and when I test drove some newer 275hp Eldos, I felt that my 270hp 94 was stronger.

I know that every car is different but I had that impression more than once. Thanks for the reply

[Cadillac Jim]

The exact torque of any given engine is a function of many things. The most important is the preloads for tuning conditions and shift points that the dealer can change with a Tech II. After inquiring about "a chip" a few times, I was informed that they had "reprogrammed my PCM" and a little smoothness went away in favor of noticeably better throttle response. I think that's not uncommon.

The Seville had a body change in 1998 that made it 250 pounds heavier and a couple of tenths of a second slower in the 0-60 mph times. Even in the 1992-1997 years the Seville is about 250 pounds heavier than the Eldorado.

I've heard it before that some 1993 and 1994 Northstars are noticeably stronger than later models. I can't comment because I have no personal knowledge of that. It may be that *all* of the early Northstars had their tuning parameters set for performance and that presets for smoothness were made the standard and default later, it might be a weight difference, a change in the exhaust that made the bottom end (i.e. throttle response in most normal driving) more responsive but didn't affect the peak torque or horsepower, or whatever.

[airmike]

I saw a test article done on chrysler 426 hemi engines many years ago, that had 10 engines all identical. They were all dyno tested and produced different horsepower. I cant recall the total variance, but it seems like it was 25 hp from the lowest to the highest. In any case they swapped the head from one to the other with the same results. ex-blk one had highest hp, blk ten had lowesst hp. they changed cams, intakes etc.. until all parts had been interchanged and the 1st block that had the highest hp continued to have the highest hp.

The point of this is that just because an engine is rated at x amount of horsepower there can be a significant variance. I believe the rating is supposed to be minumum hp expected to be produced by an engine.

[Cadillac Jim]

The Chrysler 426 was produced in low volumes for Chrysler to their specs by Mercury Marine in Oklahoma, as the original all-aluminum DOHC ZR-1 engine for the Corvette was manufactured under GM specs for GM. It is basically a high-deck large block Chrysler (the 383 was a low-deck large block Chrysler, the 440 was a high-deck large block Chrysler) with 426-specific heads. It had two major flaws that together made its availability short: it weighed 950 pounds and no aluminum heads or block were available, and cooling was insufficient to allow full output for more than... seventeen seconds, a little more than enough to propel any car it was sold in through a quarter mile. But with its hemi head design and massive ports (the intake valve guides went through the intake ports) it had more potential for horsepower than the other seven-liter engines of the time, though.

Why the horsepower followed the block in the tests that airmike read about surprises me. I would expect that it would follow the heads. The only thing unique about a block is accuracy of the bores and crankshaft/camshaft alignment under stress. So, apparently, this difference hass more of an effect than any small differences in the other parts in a 426.

Mercury Marine makes its own blocks for its Outdrive series to the specs of several of the auto sources, including bowtie small and big block, Ford, and Chrysler, probably to adapt the cooling to marine use, so they are no stranger to block and head castings. Their best-selling V8 for years was the Oldsmobile 350, or at least their castings with Oldsmobile internals. In the late 1950's, I rode in a boat with twin Cadillac V8's, although I don't know if this was a Mercury Marine installation or not.

[WarrenJ]

Don't want to get more horses, just was curious. I had been looking around for a while and when I test drove some newer 275hp Eldos, I felt that my 270hp 94 was stronger.

I know that every car is different but I had that impression more than once. Thanks for the reply

Your "feeling" is justified. The published 0-60 times for the earlier Northstars are close to a second faster than later years. My '95 Sport Coupe was noticeably faster than my '98 Sport Coupe and I'd bet the '95 would take my current 300hp Touring Coupe in a 0-60 run, though not in a 50-80 or a 50-100 skirmish.

The '95 also had a slightly louder exhaust note that I miss. I also liked the way it would chirp the tires and threaten to get slightly "out of shape" when shifting second. While that was a hoot, it wasn't something I ever tried on a wet road!

[Texas Jim]

Don't want to get more horses, just was curious. I had been looking around for a while and when I test drove some newer 275hp Eldos, I felt that my 270hp 94 was stronger.

I know that every car is different but I had that impression more than once. Thanks for the reply

Your "feeling" is justified. The published 0-60 times for the earlier Northstars are close to a second faster than later years. My '95 Sport Coupe was noticeably faster than my '98 Sport Coupe and I'd bet the '95 would take my current 300hp Touring Coupe in a 0-60 run, though not in a 50-80 or a 50-100 skirmish.

The '95 also had a slightly louder exhaust note that I miss.

I also liked the way it would chirp the tires and threaten to get slightly "out of shape" when shifting second. While that was a hoot, it wasn't something I ever tried on a wet road!

Speaking of that... chirping the tires...

I have wondered what is different about different brands of tires.

I suppose it is just the different tread compounds

Some of them will squall when they spin or you take a curve too fast... some of them make no sound at all.

The BF Goodrich on my 2006 Chevy will make noise....

The Yokohama's on my Cadillac make no noise at all... which is probably a good thing... :)

Just something I have wondered about.......

[navion]

I had a 1994 SLS that seemed really strong and got very good mileage. I replaced it with a 2003 SLS. The 2003 is not as strong as the 1994 and the mileage is not quite as good. BUT the 2003 will run on regular while the '94 was much happier with premium fuel. The bottom line is that the 2003 has a better MPD, (miles per dollar) than the '94.

Other than not being as strong as the '94, my main complaint is that the 2003 seats aren't nearly as comfortable as the '94's were.

[airmike]

Jims_97_ETC..

Back to the blocks having the horsepower difference, the thing was cylinder distortion. Racers look for seasoned blocks and use sonic testing to measure thickness of cylinder castings. I believe that is also the reasoning for some race engines having no water and the water jackets filled.

[Cadillac Jim]

I wondered about the block filler that I see in the Summitt Racing catalogs. Thanks for the information.

[Ranger]

FWIW, the pre '96 L37's also had stronger exhaust valve springs. I think that was due to the higher redline. What difference (if any) that made I do not know.